<template>
  <div class="spec-preview">
    <img :src="skuImageList[defaultIndex]?.imgUrl" />
    <div class="event" @mousemove="zoomMouseMove"></div>
    <div class="big" >
      <img :src="skuImageList[defaultIndex]?.imgUrl" ref="bigImg"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props:["skuImageList", "defaultIndex"],
    methods:{
      zoomMouseMove(e){
        //获取鼠标达到容器边缘的距离
        const mouseToBox = {
          x : e.offsetX,
          y : e.offsetY
        }
        //获取蒙版的一半的宽度
        const masKWH = {
          w : this.$refs.mask.offsetWidth / 2,
          h : this.$refs.mask.offsetHeight / 2
        }

        //计算蒙版需要移动的距离
        const maskLocation = {
          x : mouseToBox.x - masKWH.w,
          y : mouseToBox.y - masKWH.h
        }

        //临界值判断
        if(maskLocation.x <= 0){
          maskLocation.x = 0
        }else if(maskLocation.x >= e.target.clientWidth - this.$refs.mask.offsetWidth){
          maskLocation.x = e.target.clientWidth - this.$refs.mask.offsetWidth
        }

        if(maskLocation.y < 0){
          maskLocation.y = 0
        }else if(maskLocation.y >= e.target.clientHeight - this.$refs.mask.offsetHeight){
          maskLocation.y = e.target.clientHeight - this.$refs.mask.offsetHeight
        }

        //赋值
        this.$refs.mask.style.top = maskLocation.y + "px";
        this.$refs.mask.style.left = maskLocation.x + "px";

        //经计算比例是2，给大图移动赋值
        this.$refs.bigImg.style.left = - maskLocation.x * 2 + "px";
        this.$refs.bigImg.style.top = - maskLocation.y * 2 + "px";
    },
      }
    }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>